DESCRIPTION: This proposal involves multinuclear, multifield, and multiphase NMR investigations of the metal sites in metalloproteins. The primary metal nuclei that will be examined are 113Cd and 67Zn. The work with 113Cd continues successful use of Cd2+ as a "spin spy" for the function of Zn2+ in carboxypeptidase and for probing protoporphyrin dependent proteins, such as hemoglobin. Low temperature 67Zn NMR experiments on carboxypeptidase will be performed to test the strategy of replacing Zn2+ with Cd2+. New model compounds of cadmium with a variety of coordination environments will be synthesized and studied by solution and single crystal NMR. Emphasis will be given to the preparation of ionic compounds that hold the promise of yielding crystals sufficiently large for single crystal NMR experiments that can provide 113Cd shielding tensors. Development of ab initio MO methods for calculating these tensors will continue in parallel with the experimental efforts to guide interpretation of the NMR data.